I think you should be fine. Most repetitive injuries come from doing the same thing over and over and over for hours on end. You are probably more likely to get stress injuries from prolonged typing.
I used to take Taekwondo and we would do drills where we would bang forearms against each other in order to toughen them since we used our forearms for blocking. I never had problems with it.
My uncle is a weight trainer and has also trained in several different martial arts throughout his life (he is 55 now) and his only long-lasting injury is that he no longer has feeling in his fingertips; the nerves are shot from banging his fingertips against stuff. I'd imagine that could also be avoided with proper training.